The invention relates generally to contaminant control systems and more particularly to a bag-like work module which enables workers to work in an enclosed workspace without physical contact with contaminants in the workspace.
In nuclear power plants, steam generators typically are utilized as heat exchangers between the reactor and a power generating steam turbine. The steam generators have hundreds or thousands of heat exchange tubes in single pass or double pass loop tubes inside the generator housing. The tubes carry uncontaminated water through the generators which is converted into steam to drive the turbine by hot water from the reactor flowing around the outside of the heat exchange tubes. Periodically, typically during a reactor refueling outage, or if a leak occurs, the tubes are checked to make sure they are not leaking or stressing to the point where they will leak.
The tubes are checked by running a tester, typically an eddy current tester, over the length of each tube to be checked. Typically, unless a leak has occurred, some predetermined number of the thousands of tubes are checked during each outage so that during a period of time all the tubes are checked. The testers are operated, repairs or sealing off of leaking tubes are performed by workers physically climbing into the steam generators through a manway or portal in the generator housing. The interior of the generators, which typically are sixty feet high, is full of contaminants from the reactor water which are on the interior surfaces of the housing and are dislodged by the workers themselves from the tubes and surfaces. This causes surface contamination of the worker's garments, which contamination is then brought out of the generator when the workers climb out of the portal.
Further complicating the problem, is the fact that the interior or workspace of the generator is radioactive and the workers are only permitted to be inside the generator for a few minutes at a time. The checking and repairs may require hundreds of entrances and exits during a refueling outage of eight weeks. The generators typically are worked on for two weeks out of an eight week refueling outage.
Each worker typically is attired in several layers of clothing covered by a plastic outer layer and a self contained breathing apparatus. This makes it difficult to pass through the portals, which usually are small on the order of sixteen inches in diameter, and the clothing itself is cumbersome to work in.
Further, each time the worker leaves the generator at least the outer clothing which has radioactive contaminants on it has to be removed and disposed of. The area around the portal becomes contaminated and must be cleaned. The workers outside the generator are exposed to the contaminants brought out on the clothing and the worker himself is further exposed because the contaminants are in physical contact with the clothing and remain there while the clothing is further handled and disposed of.
The invention permits workers to work in a cool, comfortable environment without cumbersome extra clothing and air masks. The workers pass into and out of the module of the invention without physical exposure to the contaminants and without carrying contaminants outside the workspace. Thus, the length of exposure to the workers is reduced, the amount of material to be disposed of is greatly reduced and contamination of workers and outside areas are substantially eliminated. Further, the contaminants are not handled when the job is finished because the module is inverted and disposed of with the contaminants enclosed therein.